Common rail fuel systems are one of several diesel engine fuel systems used to improve diesel engine emissions and performance. Common rail fuel systems include a common rail supplying fuel to a plurality of fuel injectors. At least a part of these fuel injectors are maintained at rail pressure, while another part of the fuel injectors are kept at low pressures. The pressure differential between the various parts of the fuel injectors can create potential leakage paths.
Leakage paths allow fuel to travel from high-pressure regions to low pressure regions. Any leakage of fuel that occurs at these higher fuel pressures tends to generate heat in the vicinity of the leakage path and the heat is transferred to the injector components.
In addition to the increased pressures inside fuel injectors, diesel engine manufacturers have been utilizing multiple injections of fuel into the combustion chamber during any particular combustion phase to meet the increasingly stringent emissions regulations. In most cases, multiple injections are achieved by electrically energizing an actuator (e.g., solenoids, piezo-electric actuators, etc.) that controls the movement of a valve multiple times during each combustion cycle. To accomplish these multiple actuation events, more electrical energy is required. However, the increase in electrical energy supplied to the actuator often results in an increase in the heat energy that is generated. This is especially problematic in connection with the use of solenoids, which tend to be susceptible to uncertain or degraded behavior at temperatures that can be easily reached if the fuel injector is not sufficiently cooled.
It has been known in the prior art that external cooling liquids may be used to cool overheated engine components. U.S. Pat. No. 4,553,059 (known as the '059 patent) provides insight for cooling a piezoelectric actuator that may be degraded when the temperature of the piezoelectric element becomes higher than a Curie point. In the '059 patent, the piezoelectric element experienced an increase in temperature through the repeated energization of the piezoelectric elements during injection events. The '059 patent teaches the use of an external cooling liquid to cool the piezoelectric actuator by allowing the liquid to flow around the actuator.
The present disclosure is directed to overcoming one or more of the problems set forth above.